Energy is the most important element in the human economic activities. The energy is a natural resource and comes from radiation from the sun. Coal, petroleum and natural gas are solar energy stored in living beings in ancient times, and they are mainly hydrocarbons. Water and air may produce huge potential energy and kinetic energy under the action of the solar energy, and electric power converted from such potential energy and kinetic energy can become power for all machines. Water and wind can be directly converted into electric power, and such conversion will not produce environmental pollutants. The combustion of coal, petroleum and natural gas releases huge heat to thereby produce power. However, the combustion process produces a large number of environmental pollutants, e.g., carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen oxide, carbon black particles, etc., and these environmental pollutants destroy the living environment of the human beings and endanger the human health. Further, since these energies are nonrenewable, along with the increase of the energy consumption day by day, and the decrease of the energy day by day, these energies will be exhausted one day. Thus, in the context that the problems of energy and environment are increasingly prominent, close attention is paid all over the world to seeking of clean and renewable new energy to replace the traditional fossil energy.
In the research on various new energies, hydrogen gas becomes the first choice of the researcher with its completely clean combustion manner and advantage of renewability. The hydrogen gas, as an ideal new energy, holds the following characteristics:
1. The heat release rate of hydrogen gas is high. Concretely, 140,000 joules of heat can be released by means of combustion of a gram of hydrogen gas, which is equivalent to approximately three times of the heat released by means of combustion of a gram of gasoline, and also the hydrogen gas can be recycled.
2. Water is the main raw material used for making hydrogen gas, and there are two hydrogen atoms in just one molecule of water; and water covers 71% of the earth surface and the resource is very rich.
3. In the combustion process of the hydrogen gas, in addition to huge energy released, the product of the combustion is only water, with no pollution emission and the combustion process will not cause environmental pollution, so the hydrogen gas is also called “clean energy”.
4. The hydrogen gas is light in weight, small in density, convenient in transport and carriage, and easy in storage, which has a more remarkable advantage over electricity that is difficult to be stored.
5. The use of the hydrogen gas is extremely broad. Specifically, the hydrogen gas is not only capable of producing heat energy by combustion process, but also producing various hydrogen-containing compounds, and further serve as the working medium for absorbing heat and the like.
Although the hydrogen energy takes so many advantages as mentioned above, at present, the development of hydrogen energy is restricted due to the expensive cost for producing the hydrogen gas. The traditional preparation methods of hydrogen include preparation of hydrogen by electrolyzing water and preparation of hydrogen by a high pressure or a high temperature, which need to consume a large amount of electric energy and coal or natural gas. The consumed energy is more than the energy produced by means of the combustion of the fuel. Such expensive cost makes the hydrogen energy be only adapted to special uses, e.g., promoting the space rocket or maintaining the fuel cell in the spacecraft. Thus, it has not been truly achieved yet although many researchers put forward the fancy of producing hydrogen energy by water for many years.